Transmissible spongiform encephalopathies (TSEs), also termed prion diseases, are a threat to food safety and to human and animal health. Variant Creutzfeldt-Jakob disease (vCJD) in humans is caused by the consumption of meat contaminated with bovine spongiform encephalopathy (BSE, mad cow disease). The BSE epidemic in the United Kingdom was shown to be related with the extensive use of BSE-contaminated meat-and-bone meal (MBM) and bovine offal. Many countries worldwide use MBM, as well as meat from cows, for aquaculture feed. This raises concerns about the safety of farmed fish, a major protein source for humans. The present work reviews recent studies on fish prion protein and the transmissibility of mammalian prion agents to fish, providing insights into the future direction of fish prion research.

This study examined the effects of additives on the physical properties of surimi made from Antarctic krill Euphausia superba. Krill surimi was prepared from krill meat with an added cryoprotectant (sugar 6%, polyphosphate 0.2%). Krill surimi without additives does not form a gel. In order to enhance the gelling of krill surimi, additives such as soy protein isolate (SPI), guar gum, carrageenan, and wheat starch were examined. Of these, SPI had the highest gel-forming activity, while guar gum, carrageenan, and wheat starch had decreasing gel-forming activity and negative effects on other physical properties as their concentrations were increased. In addition, SPI enhanced the gel strength and physical properties of krill surimi. The fluoride and astaxanthin contents of krill surimi with added SPI were 55.0 mg/kg and 0.8 mg/kg, respectively.

Phlorotannins, the major constituent in brown algae, possess various biological activities; however, there is little information their toxicological effects. To assess the safety of phlorotannins, we investigated the acute oral toxicity of a high-purity phlorotannin preparation (PRT; total phlorotannin content 90%) in beagle dogs. Six beagle dogs (3 males, 3 females) were assigned randomly to three experimental groups. PRT was administered at oral doses of 250, 500, and 750 mg/kg by capsule. Vomiting by male and female beagles was observed with 500 and 750 mg/kg on the first day. In addition, one beagle given 750 mg/kg had soft stool and diarrhea on days 3 and 13. No deaths or abnormal clinical signs were observed during the experiment. All groups showed similar body weight gain and food consumption. Our acute toxicity study showed that PRT did not cause any toxicological effects in beagle dogs.

Obesity is a worldwide problem that contributes to serious diseases, including diabetes, hypertension, and atherosclerosis. Recently, much research has examined functional natural materials and their anti-obesity activity. This study investigated the effect of enzyme-treated Ecklonia cava extracts on mice fed a high fat diet. To test the anti-obesity effects of a diet containing the enzyme-treated E. cava extracts (EEc), C57BL/6NTacSam mice were divided into six groups : normal diet (ND), high-fat diet (HFD), high-fat with Garcinia extract diet (GHD), and three high-fat with EEc diet (EHD250, EHD500, and EHD1000) groups. After 9 weeks, body weight was increased significantly in the HFD group compared to all of the EHD groups, and the weights of the liver, perirenal fat and epididymal fat paralleled the increase in body weight. The serum GOT, GPT, triglyceride, total cholesterol, and LDL-cholesterol levels were lower in the EHD1000 group than in the HFD group. The glucose and leptin concentrations were lowest in the EHD1000 group and C/EBP family expression was decreased in a dose-dependent manner. These results indicate that E. cava extracts not only have anti-oxidation functions but also anti-obesity effects.

BACE2 is a membrane-bound aspartic protease that is highly homologous with BACE1. While BACE1 processes the amyloid precursor protein (APP) at a key step in generating -amyloid peptide and presumably causes Alzheimer`s disease (AD), BACE2 has not been demonstrated to be involved in APP processing directly, and its physiological functions are unknown. To determine its function and to develop inhibitors from marine sources, we constructed an overexpression vector for producing BACE2. The gene encoding human BACE2 protease was amplified using the polymerase chain reaction and cloned into the pET11a expression vector, resulting in pET11a/BACE2. Recombinant BACE2 protease was overexpressed successfully in E. coli as inclusion bodies, refolded using the rapid-dilution method, and purified via two-step fast protein liquid chromatography using Sephacryl S-300 gel filtration and Resource-Q column chromatography. The BACE2 protease produced was an active form. This study provides an efficient method not only for studying the basic properties of BACE2, but also for developing inhibitors from natural marine sources.

This study determined the level of fermented soybean meal (FSM) that could be substituted for fish meal in the diet for parrot fish Oplegnathus fasciatus. Fish meal (FM) was used the sole protein source in the control diet. FSM was substituted for 20, 40, 60, 80, and 100% of the fish meal in the experimental diets. The FSM resulted in increased crude protein, crude fat, and crude ash, but decreased crude fiber. The methionine and tryptophan contents in the FSM increased, while lysine and threonine decreased. The 18:2n-6 fatty acid content decreased from 55.30% to 28.67%. Fermentation increased 20:5n-3 (EPA) and 22:6n-3 (DHA) by 2.03% and 15.54%, respectively, although the differences were not significant. Based on growth performance, we concluded that FSM could replace up to 60% of FM for the maximum growth of juvenile parrot fish.

We conducted an 8-week feeding trial to evaluate dietary lipid sources on the growth performance and body composition of juvenile river puffer fish Takifugu obscurus. Nine experimental diets were formulated with fishmeal as the major protein ingredients, providing 50% crude protein. The experimental diets contained either beef fallow (BF), soybean oil (SO), rapeseed oil (RO), or linseed oil (LO). Each of these diets was then supplemented or not with 0.5% n-3 HUFA (BFH, SOH, ROH, and LOH), resulting in a total of eight experimental diets. The control diet contained fish oil (FO) as the lipid source. Fish averaging were fed the experimental diets in randomly selected triplicate groups for 8 weeks. Weight gain and feeding efficiency of fish fed the FO and SOH diets were significantly higher than those of fish fed BF or RO (P<0.05), but these diets did not differ significantly from the other diets. The protein efficiency ratio of fish fed the SOH diet was significantly higher than that of fish fed the BF, SO, or RO diets (P<0.05), but these were not significantly different from the other diets. The specific growth rate of fish fed the FO and SOH diets was significantly higher than that of fish fed the BF diet (P<0.05). Whole body DHA and n-3 HUFA contents of fish fed the FO diet were significantly higher than those of fish fed the SO, RO, or LO diets (P<0.05), but were not significantly different from the other diets. These results indicate that soybean oil and linseed oil could replace up to 100% of fish oil in the diet containing 60% fishmeal for river puffer fish.

We investigated the effects of feeding rate on the growth performance, blood components, and histology of growing olive flounder Paralichthys olivaceus. Optimum feeding rate (initial fish mean weight : ) was determined under the optimum water temperature. Two replicated groups of fish were fed a commercial diet at rates of 0%, 0.4%, 0.6%, and 0.8% of body weight (BW) per day, and to satiation. Feeding trial was conducted using a flow-through system with 10 1.2-metric ton aquaria receiving filtered seawater at for 3 weeks. Weight gain (WG) and specific growth rate (SGR) were significantly higher in fish fed to satiation (1.0% BW/day) than in those in other treatments. These parameters were negative and significantly lower in the starved fish than in fish fed the experimental diet at all feeding rates. There were no significant differences in WG and SGR among fish fed at 0.4%, 0.6%, and 0.8% BW/day. Hematocrit and hemoglobin in fish fed to satiation were significantly lower than those in other treatments. Histological changes of fish fed at 0.6% BW/day indicated that this group was in the best condition; differences were not found in tissues of fish fed at 0%, 0.6% and 1.0% BW/day. Broken-line regression analysis of weight gain showed that the optimum feeding rate of olive flounder weighing 317 g was 0.99% BW per day at the optimum water temperature.

To evaluate the influence of burrowing substrate on the rearing performance and ambicoloration of cultured flounder, Paralichthys olivaceus, we compared the daily food intake (DFI), feed efficiency (FE), survival, growth, proportion of pigmented skin on the blind side, and proportion of ambicolored fish. We reared juvenile flounders [total length (TL) , body weight (BW) ] in dark-green fiberglass-reinforced plastic (FRP) aquariums without (control) or with gravel substrate at a density of 200 fishes/ton for 120 days. While there was no difference in survival rate or growth, the DFI was lower and FE higher in the group raised with substrate than in the control. The proportions of pigmented area on the blind side and ambicolored fish were significantly higher in the control tank. Therefore, the supplement of substrate on the aquarium bottom positively affects the feeding efficiency, and inhibits abnormal pigmentation on the blind side in flounder farming at high density.

The effect of a bopyrid isopod Argeia pugettensis, on the growth and reproduction of the Kuro shrimp Argis lar was investigated. A commercial caridean shrimp in the East Sea of Korea, A. lar, was sampled monthly off Pohang with a bottom trawl from July 2009 to June 2011. During the study period, 7,988 individuals were sampled. These shrimp were parasitized by a bopyrid isopod Argeia pugettensis. The overall infection rate was 3.3%, although it declined in the larger size classes. It did not change monthly. The carapace lengths of the host and parasite were positively correlated. There was a significant difference in growth between infested and non-infested shrimp. The infested shrimp also had a lower gonadosomatic index (GSI) and breeding rate. These results suggest that the parasites affected the growth and reproduction of Argis lar.

We consider changes in the fishing ground of the small yellow croaker Larimichthys polyactis and discuss their utility in predicting fishing conditions for this species. The fishing ground, which having been formed around Jeju Island since the 1970s, is dominated by the Yellow Sea Bottom Cold Water (YSBCW), and variation in its southward expansion from the Yellow Sea is the single most key environmental factor affecting the L. polyactis catch. When the YSBCW showed strong expansion and the fishing ground shifted to the west and southwest of Jeju Island, as occurred in the late 1980s, late 1990s, and early 2000s, the L. polyactis catch was low; conversely, when expansion was weak, as in the early 1990s and late 2000s, the L. polyactis catch was high. This relationship was statistically significant and should be useful in predicting fishing conditions for L. polyactis.

Two major temperature fronts, the Subpolar (Gosung, Gang-won-do; ) and Thermal (Jukbyun, Gyeong-sang-buk-do; ) fronts, are found in the East Sea along the east coast of Korea. These are located roughly where the Tsushima Warm Current and North Korea Cold Current intersect. To clarify the effect of the Thermal Front, we investigated seasonal variation in fish species composition using set nets in two areas located north (Jangho, Gang-won-do) and south (Hupo, Gyeong-sang-buk-do) of Jukbyun, Gyeong-sang-buk-do, and compared the sea water temperature and salinity. We collected a total of 38 fish species in Hupo and 25 in Jangho. Trachurus japonicus was the most common species at both sites, but the subdominant species differed. At Hupo, the subdominant species were Konosirus punctatus and Diodon holocanthus, whereas Clupea pallasii and Scomber japonicus were subdominant at Jangho. Based on Froese and Pauly (2014), subtropical fishes accounted for 55% of fish in Hupo but only for 33% in Jangho. The difference in fish species composition was most obvious in May and August. According to the Korea Hydrographic and Oceanographic Administration, sea surface temperature and salinity were slightly higher at Hupo than at Jangho. Our findings suggest that the oceanographic boundary resulting from the Thermal Front near Jukbyun, Gyeong-sang-bukdo may have a major effect on the distribution of migratory fish species.

Cytogenetic analysis was conducted to obtain basic information for chromosome manipulation of starry flounder Platichthys stellatus. Nuclear surface area and volume of erythrocyte were and , respectively. The haploid DNA content of the species was 0.66 pg/haploid cell which correspond to 93% of olive flounder Paralichthys olivaceus. A karyotype analysis was also carried out with the species using conventional staining and Ag-NOR banding techniques. It was consisted of 48 acrocentric chromosomes and inter-sex or intra-individual polymorphism was not detected in all specimens analyzed. The NOR regions, appearing a terminal position of the short arm of the smallest acrocentric pairs.